1. Field of the Invention
The present invention relates to reverberation devices and more particularly to such devices having a feedback delay line.
2. Description of the Prior Art
Electronic reverberation devices are used for achieving special effects in generating, recording or reproducing sound events, at least approximately simulating the reverberant sound effects of a larger room. Such reverberation devices are used, for example, in electronic organs.
As disclosed in an article by M. R. Schroeder in the "Journal of the Audio Engineering Society" (July, 1962), Vol. 10, No. 3, pp. 219 to 223, a simple electronic reverberation device according to FIG. 1 can be formed in such a way that the signal which is intended to die away, is fed to a delay line D, and that the output signal, via an amplifier with the gain g &lt; 1 and a linear adder circuit A, is re-applied to the input of the line. The degree of amplification g is determined by the required reverberation time and by the delay time of the employed delay line.
It is described by M. R. Schroeder that the frequency-dependent phase position of the output signal of the delay line in a reverberation device according to FIG. 2, causes the reverberation device to have an interdigitated filter characteristic. The author, without actually implying same, proceeds in his considerations from the fact that the amount of the line attenuation .vertline.g.sub.d .vertline. = 1. This, however, is not the case in practice, in fact, known types of delay lines, whether mechanical, acoustic, electromagnetic or electronic, all have a frequency-dependent attenuation .vertline.g.sub.d .vertline. = .phi. (f). Therefore, in the circuit arrangement as disclosed by M. R. Schroeder, the output signal of the reverberation device as well as the reverberation time will show an unwanted frequency response.